Decoder and encoder for a digital fingerprint code

ABSTRACT

A method to encode and decode a digital fingerprint code by an identification encoder and an identification decoder wherein the digital fingerprint code includes a plurality of N-bit data embedded on a set of curves by changed thicknesses in the curves.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 National Stage Application ofPCT/EP2015/055536, filed Mar. 17, 2015. This application claims thebenefit of European Application No. 14160243.3, filed Mar. 17, 2014,which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention pertains generally in the technical field of encoding anddecoding optical-machine-readable reproductions of information, alsocalled identification codes, which are readable by a digital imagingdevice, such as digital camera in a mobile phone.

2. Description of the Related Art

Different types of identification codes are well-known, especially inthe graphical industry. One of the oldest types of opticalmachine-readable reproductions is the one-dimensional barcode. Theseone-dimensional barcodes are representing the data by varying the widthsand spacing's of parallel lines. Barcodes originally were scanned byspecial optical scanners, called barcode readers. Later, digital imagingdevices and interpretive software became available on devices such asportable mobiles.

The one-dimensional barcode is nowadays evolved to two-dimensionalbarcodes, also called matrix barcodes such as the Quick Response Code orQR code. The QR code was first designed for the automotive industry inJapan. A QR code on an item is scanned by a digital imaging device toread the content about the item which it is attached.

The ability of portable mobiles to scan QR codes makes this type oftwo-dimensional barcodes popular. For example a QR code, embedded indocument markup language documents, such as HTML, contains a hyperlinkto a web page. Another example is a QR codes, printed on a package, suchas pharmaceutical package comprising a medicine, directs the operator ofa mobile phone, after the QR code is scanned, to the specifications ofthe medicine on a web page.

The current available types of identification codes, such as QR code,are conspicuous in a reproduction of a document which makes it easier tointerpret a content embedded in the optical machine-readablereproduction.

Also an identification code takes some place in a layout of the documentwhich may be used for other content. Especially in small sizedreproductions such as packages of medicines.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention have been realised with a digital fingerprintcode (DF code) which is encoded in a document as defined below anddecoded by an digital imaging device as defined below.

The preferred embodiments of the invention give the ability to addsecret or/ and invisible-for-the-human-eye content at a certain viewingdistance to a document by an identification code and it gives theability to create more space in the document space of a document to addmore content in a document. The preferred embodiments of the inventioncomprise also a method to decode the digital fingerprint code easily bya digital imaging device to read the content embedded in a digitalfingerprint code (DF code).

The digital fingerprint code comprises a set of curves wherein a content(CNT) is embedded by a plurality of N-bit data;

-   wherein each possible value of N-bit data has a thickness (T_(N,i))    and length (L_(N,i)); and-   wherein the plurality of N-bit data comprises a first N-bit data    (N₁), subsequent by a different second N-bit data (N₂) on a curve of    the set of curves; and-   wherein the thickness of the value (v_(N,1)) of the first N-bit data    (N₁) on the curve is different from the thickness (T_(N,1,2)) of the    value (v_(N,2)) of the second N-bit data (N₂) and/or-   wherein the length (L_(N,i,1)) of the value (v_(N,1)) of the first    N-bit data (N₁) on the curve is different from the length    (L_(N,i,2)) of the value (v_(N,2)) of the second N-bit data (N₂);-   wherein the digital fingerprint code is decoded by an identification    decoding method which comprises the following steps:    -   capturing a digital fingerprint code (DF code) by a digital        imaging device; and    -   determining an image captured curve in the image captured        digital fingerprint code; and    -   determining from a set of two-dimensional points (p_(k)) on the        image captured curve a set of thicknesses (t_(k)) of the image        captured curve; and    -   determining the plurality of N-bit data from the set of        thicknesses (t_(k)) and the location of the set of        two-dimensional points (p_(k)) on the image captured curve;        and/or-   wherein the digital fingerprint code is encoded by an identification    encoding method which comprises the following steps:    -   determining a document; and    -   determining a curve in the document; and    -   determining for an N-bit data of the plurality of N-bit data a        thickness (T_(N,i)) and a length (L_(N,i)); and    -   determining a first segment on the determined curve with        determined length (L_(N,i)); and    -   changing the thickness of a part in the first segment to the        determined thickness (T_(N,i)); and    -   generating from the document with the generated digital        fingerprint code a new document.

A curve is a two-dimensional continuous line which doesn't have to bestraight. A curve has a start point and an end point. The length of thecurve is preferably finite and bounded. And in a preferred embodiment acurve is a non-self-intersecting-curve. A curve in a preferredembodiment continues, uninterrupted and bounded. In a preferredembodiment the set of curves comprises one curve.

The thickness on a curve may be any shape such as triangular, quadratic,rectangular, heptagonal, pentagonal, oval, rhombus, octagonal, orelliptical shaped. The determining the thickness of a curve or a line isa well-known method wherein the thickness of the curve or line in theperpendicular direction of the curve or line is measured.

In the identification decoding method a one-dimensional signal isdetermined from the plurality of N-bit data out the set of thicknessesand the location of the set of two-dimensional points on the imagedcaptured curve, wherein the one-dimensional signal is varied with adetermined thickness in its determined location (FIG. 1, FIG. 2, FIG.3). So in a preferred embodiment the step of determining the pluralityof N-bit data from the set of thicknesses (t_(k)) and the location ofthe set of two-dimensional points (p_(k)) on the image captured curvecomprises the step of generation a one-dimensional signal based on thedetermined set of locations and corresponding thicknesses. Theone-dimensional signal is than translated to the plurality of N-bitdata, which is embedded in the digital fingerprint code. This preferredembodiment may comprise also a discretization step and/or quantizationstep to determine the plurality of N-bit data, embedded in the digitalfingerprint code.

In a preferred embodiment the identification encoding method maycomprise the following steps:

-   -   determining the following N-bit data of the N-bit data a        thickness (T_(N,i)) and a length (L_(N,i)); and    -   determining a second segment on the determined curve, following        the first segment, wherein the second segment has the determined        length of the following N-bit data; and    -   changing the thickness of a part in the second segment to the        determined thickness of the following N-bit data.

In a more preferred embodiment a third segment is determined between thefirst and second segment and third segment is determined with a fixedlength and/or with a fixed thickness. Preferably the fixed thickness isdifferent from the thicknesses (T_(N,i)) of all values of N-bit data.This makes the distinctions between following N-bit data while decodingeasier.

The identification code of a preferred embodiment is called a digitalfingerprint code (DF code).

In a preferred embodiment each possible value of N-bit data has a color(C_(N,i)); and wherein the color (C_(N,i,1)) of the value (v_(N,1)) ofthe first N-bit data (N₁) on the curve is different from the color(C_(N,i,2)) of the value (v_(N,2)) of the second N-bit data (N₂); and

-   wherein the identification decoding method comprises the step of:    -   determining in the set of two-dimensional points (p_(k)) a set        of colors (c_(k)); and    -   determining the plurality of N-bit data from the set of        thicknesses (t_(k)), the location of the set of two-dimensional        points (p_(k)) on the path and the set of colors (c_(k)); and/or        the identificiation encoding method comprises the following        steps:    -   determining for the N-bit data the color (C_(N,i)); and    -   changing the color of the segment to the determined color        (C_(N,i)).

By using colors in the digital fingerprint code (DF code) has a positiveimpact on the storage-amount on a curve, surely when the true outputresolution of the content output device is small.

The digital fingerprint code (DF code) is preferably in theidentification decoding method, image captured by a digital imagingdevice comprised in a mobile device; and wherein the mobile device isselected from a mobile computer, such as a computer tablet or mobilephone, such as a smart phone.

In a preferred embodiment the digital fingerprint code (DF code) is usedto read the content about the item on which the digital fingerprint codeis attached.

In another preferred embodiment the digital fingerprint code (DF code)is used to track-and-trace the item on which the digital fingerprintcode is attached. Track-and-trace or tracking-and-tracing, concerns aprocess of determining the current and past locations (and otherinformation) of a unique item or property.

In another preferred embodiment the digital fingerprint code (DF code)is used to add secure content for anti-counterfeiting purposes on theitem on which the digital fingerprint code is attached. Theanti-counterfeiting purposes may be enhanced wherein the item is acontainer comprising a liquid and wherein the digital fingerprint code(DF code) is reproduced with more than 50% of the compounds of theliquid by a printer device. More preferably the item is a containercomprising an inkjet ink and wherein the digital fingerprint code (DFcode) is reproduced with more than 50% of the inkjet ink by an inkjetprinter. By chemical analysis the printed liquid of the reproduceddigital fingerprint code may be compared with the liquid inside thecontainer, such as a bottle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (FIG. 1) illustrates a content by a plurality of binary data(300), which is a N-bit data wherein N is equal to 1 in a graph. On thevertical axis (100) the thickness (T_(N,i)) of a N-bit data can be read,for example in micrometers and on the horizontal axis (200) the locationon a curve from the set of curves can be read, for example inmicrometers.

The graph in FIG. 1 represents ‘1100’ as a plurality of binary data. Thethickness for value 1 (T_(N,1)) and the thickness for value 0 (T_(N,0))of a bit is different and the length for value 1 (L_(N,1)) and thethickness for value 0 (L_(N,0)) of a bit is equal. Between two sequentbinary dates a fixed thickness and fixed length is represented.

FIG. 2 (FIG. 2) illustrates a content by a plurality of binary data,which is a N-bit data wherein N is equal to 1 in a graph. On thevertical axis (100) the thickness (T_(N,i)) of a N-bit data can be read,for example in micrometers and on the horizontal axis (200) the locationon a curve from the set of curves can be read, for example inmicrometers.

The graph in FIG. 2 (FIG. 2) represents ‘100100’ as a plurality ofbinary data (300). The thickness for value 1 (T_(N,1)) and the thicknessfor value 0 (T_(N,0)) of a bit is different and the length for value 1(L_(N,1)) and the thickness for value 0 (L_(N,0)) of a bit is equal.Between two sequent binary dates there is no fixed length represented.The plurality of binary data ‘100100’ in this graph is an encodedplurality of binary data from another plurality of binary data ‘1100’wherein the value 1 in the encoded plurality of binary data represents achange in a bit of the another plurality of binary data and wherein theamount of zeros in the encoded plurality of binary data represents howmuch times the changed bit of the another plurality of binary data isrepresented. The encoded plurality of binary data is a kind ofrun-length-encoded (RLE) plurality of binary data.

FIG. 3 (FIG. 3) illustrates another representation of a plurality ofbinary data (300), which is a N-bit data wherein N is equal to 1 in agraph. On the vertical axis (100) the thickness (T_(N,i)) of a N-bitdata can be read, for example in micrometers and on the horizontal axis(200) the location on a curve from the set of curves can be read, forexample in micrometers.

The graph in FIG. 3 (FIG. 3) illustrates ‘1100’ as a plurality of binarydata. The thickness for value 1 (T_(N,1)) and the thickness for value 0(T_(N,0)) of a bit is different and the length for value 1 (L_(N,1)) andthe thickness for value 0 (L_(N,0)) of a bit is different. Between twosequent binary data's a fixed thickness and fixed length is represented.

FIG. 4 (FIG. 4) illustrates a curve (400) in the digital fingerprintcode (500) of wherein a plurality of binary data ‘1100’ is representedin the way it is defined in FIG. 3 (FIG. 3). The thickness for value 1(406, T_(N,1)) and the thickness for value 0 (405, T_(N,0)) of a bit isdifferent and the length for value 1 (406, L_(N,1)) and the length forvalue 0 (405, L_(N,0)) of a bit is different. Between two sequent binarydata's a fixed length is represented.

FIG. 5 (FIG. 5) illustrates a curve (400) in the digital fingerprintcode (500) of wherein the thickness for value 1 (406, T_(N,1)) and thethickness for value 0 (405, T_(N,0)) of a bit is different and thelength for value 1 (406, L_(N,1)) and the thickness for value 0 (405,L_(N,0)) of a bit is different. Between two sequent binary data's afixed length is represented. The plurality of binary data representscharacter ‘A’ (capital a) which is in ASCII character 65, andrepresented as a byte ‘01000001’. By using the Hamming method aserror-correcting code method the plurality of binary data embedded onthe curve (400) becomes ‘10011001101001’.

FIG. 6 (FIG. 6) illustrates a curve (400) in the digital fingerprintcode (500) of wherein the thickness for value 1 (406, T_(N,1)) and thethickness for value 0 (405, T_(N,0)) of a bit is different and thelength for value 1 (406, L_(N,1)) and the thickness for value 0 (405,L_(N,0)) of a bit is different. Between two sequent binary data's afixed length is represented. The plurality of binary data representscharacter ‘A’ (capital a) which is in ASCII character 65, andrepresented as a byte ‘01000001’. By using the Hamming method (7,4) aserror-correcting code and adding a header sequence ‘0001’ and tailsequence ‘0000’, the plurality of binary data embedded on the curve(400) becomes ‘1101001 1001100 1101001 0000000’. The curve (400) in thedigital fingerprint code (500) is a spiral.

FIG. 7 (FIG. 7) illustrates a part of the identification decoding methodcomprising the processing of an example to decode digital fingerprintcode with embedded content on a spiral. In a first step the digitalfingerprint code is captured by a digital imaging device (602) whichresults for the example in image captured digital fingerprint code(605). By thresholding the captured digital fingerprint code (612), assecond step, results for the example in a thresholded image captureddigital fingerprint code (615). In the third step a blurring method isperformed (622) which results for the example in a blurred imagecaptured digital fingerprint code (625). The fourth step is performing adilatation (632) to result for the example to a dilatational blurredthresholded image captured digital fingerprint code (635). After thisstep the image captured curve in the image captured digital fingerprintcode is determined.

FIG. 8 (FIG. 8) illustrates a digital fingerprint code (DF code) (500)with one spiral as curve (400) wherein the thickness for value 1 (406,T_(N,1)) and the thickness for value 0 (405, T_(N,0)) of a bit isdifferent and the length for value 1 (406, L_(N,1)) and the thicknessfor value 0 (405, L_(N,0)) of a bit is different. Between two sequentbinary data's a fixed length is represented.

FIG. 9 (FIG. 9) illustrates a digital fingerprint code (DF code) (500)with a plurality of curves (400) wherein the thickness for value 1 (406,T_(N,1)) and the thickness for value (405, T_(N,0)) of a bit isdifferent and the length for value 1 (406, L_(N,1)) and the thicknessfor value 0 (405, L_(N,0)) of a bit is different. Between two sequentbinary data's a fixed length is represented.

FIG. 10 illustrates an user interface (910) of a preferredidentification encoder comprising a plurality of user interface objects(900, 901, 902, 903, 904, 905, 906, 907, 908, 909). The user interfaceobject (909) is the title bar of a window which comprises a closingbutton (‘X’) to close the user interface (910). The user interface 901defines two input fields to define the width and the height, both inpixels, of a digital fingerprint code (DF code). The user interfaceobject (902) comprises a plurality of input fields such as the thicknessand length of value 1 (‘one bit’) and the thickness and length of value0 (‘zero bit’) and the length between two sequent binary data's. Theuser interface object (903) comprises an input field for the curvatureof the spiral as curve in the digital fingerprint code. The userinterface object (904) comprises an input field for the content that hasto be embedded in the digital fingerprint code (DF code). The userinterface object (905) comprises a check box if the content has to beencrypted with a key which has to be filled in an input field. The userinterface object (906) defines the shape of the curve: spiral-shaped orsinus-shaped (‘sine’). The user interface object (907) comprises animage which is a representation of the generated digital fingerprintcode (DF code). The user interface object (908) comprises the name(‘encrypted.jpg’) and the place of the digital fingerprint code (DFcode) on a hard disk drive (HDD) and the user interface object (909)comprises a button to start the generation of a digital fingerprint code(DF code).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Definitions Document

A document comprises content, preferably graphically arranged, in adocument space. A document is digital stored in a storage unit such ashard disk drive (HDD) connected to a hardware configuration such as acomputer, memory in a central processing unit (CPU) comprised in ahardware configuration and the like. The graphically arrangement, alsocalled lay-outing, of the content in the document space is also calledthe lay-out of the document.

A document may comprise a static layout or preferably a dynamic layout.Static layout design may involve more graphic design and visual artskills; whereas dynamic layout design may involve more interactivedesign and content management skills to thoroughly anticipate contentvariation.

The document space of the document may be a two-dimensional space withtwo fixed dimensions, more preferably the document space is a page ormultiple pages and most preferably a web-page.

The document space may be a two-dimensional space with one fixed and oneendless dimension such as in the rendering method of multiple print jobsdisclosed in EP 1933257 (Agfa Graphics NV).

The content objects in a document may be defined in one or more colorsby one or more content objects such as photographic images, businessgraphs, text, labels and the like, which are also called objects of thedocument.

A raster graphic is also known as a bitmap, contone or a bitmappedgraphic and represent a two-dimensional discrete image P(x,y).

A vector graphic, also known as object-oriented graphic, usesgeometrical primitives such as points, lines, curves, and shapes orpolygon(s), which are all based on mathematical expressions, torepresent an image.

A content object in a document may be defined in a vector graphicsformat, also called line-work format, such as Scale Vector Graphics(SVG) or AutoCad Drawing Exchange Format (DXF) and more preferablydefined in a page description language (PDL) such as Printer CommandLanguage (PCL): developed by Hewlett Packard, Postscript (PS): developedby Adobe Systems or Portable Document Format (PDF): developed by AdobeSystems. Preferably the lay-out of the document is created in a desktoppublishing (DTP) software package such as Adobe InDesign™, AdobePageMaker™, QuarkXpress™ or Scribus (http://scribus.net/canvas/Scribus).

The content objects in a document may be defined in a document markuplanguage, also called mark-up language, such as IBM's Generalized MarkupLanguage (GML) or Standard Generalized Markup Language (ISO 8879:1986SGML), more preferably defined in HyperText Markup Language (HTML) andmost preferably defined in HTML5, the fifth revision of the HTMLstandard (created in 1990 and standardized as HTML 4 as of 1997) and, asof December 2012, is a candidate recommendation of the World Wide WebConsortium (W3C). Such a document is sometimes called a web-document.

The layout of a web-document may be created in a web-design softwarepackage by Cascading Style Sheets (CSS), a style sheet language used fordescribing the content of the document in the document markup languageand more preferably the layout of a web-document is created in aweb-design software package by Cascading Style Sheets 3 (CSS3),published from the CSS Working Group of the World Wide Web Consortium(W3C).

The content objects in a document may be defined in a Variable DataPrinting format (VDP) such as Intelligent Printer Data Streams (IPDS):found in the AS400 and IBM mainframe environments and used with dotmatrix printers, Variable data Intelligent PostScript Printware (VIPP):A proprietary VDP language from Xerox, traditionally used in thetransactional black-and-white printing market, Variable PrintSpecification (VPS): a VDP language from Creo, Advanced FunctionPresentation (AFP) format defined by AFP Consortium (AFPC), morepreferably defined in Personalized Print Markup Language (PPML), anXML-based industry standard printer language for variable data printingdefined by Printing On Demand Initiative (PODi) and most preferablydefined in PDF/VT published in 2010 as ISO 16612-2.

In a preferred embodiment a document is defined in a document formatselected from vector graphic formats, document markup language orvariable data printing format, more preferably selected from pagedescription formats, variable data printing format or document markuplanguage and most preferably selected from Portable Document Format(PDF) or the fifth revision of HyperText Markup Language (HTML5).

Raster Image Processing Method

A raster image processing method is an image manipulation method thatinterpret a document to render the interpretation of the document to:

-   -   a raster graphic which is suitable for viewing on a display        device such as a television, computer monitors or the display        device of a tablet computer or mobile phone; or    -   a raster graphic which is suitable for projecting the raster        graphic by a projector device such as a video-projector, LCD        projector, DLP projector LED projector or laser diode projector;        or    -   a raster graphic which is suitable for printing on a printer        device such as a toner-based printer, an inkjet printer or        offset press.

A content output device is a device which reproduces the content data ofa document in its document space such as a display device, projectordevice or printer device.

The digital fingerprint code may be reproduced by a raster imageprocessing method on a content output device. Preferably the digitalfingerprint code is reproduced by a projecting method on a projectordevice, more preferably by a displaying method on a display device andmost preferably by a printing method on a printer device.

A raster image method is a computer implemented method that is performedon a hardware (HW) configuration, such as a computer, tablet computerand the like, comprising a central processing unit (CPU), a memory, astorage device such as a hard disk drive (HDD), a communicationinterface (IF) device that sends and receives data to and from otherhardware configurations via a network. The hardware configuration maycomprise a user interface (UI) device that may comprise a displaydevice.

The apparatus that performs a raster image processing method is called araster image processor (RIP). A raster image processor (RIP) maycomprise a prepress workflow system such as Prinect Workflow System™from Heidelberger Druckmaschinen AG or Apogee Prepress™ from AgfaGraphics NV or the prepress workflow system disclosed in US20130194598(FUJI XEROX).

In a preferred embodiment a raster image processor comprises one or moreGPU's for faster rendering a document to a content output device.

Identification Encoder

An identification encoder is a device that generates digital fingerprintcodes in a document, for example to identify an item whereon a digitalfingerprint code (DF code) in a reproduced document is attached, forexample on a label. The digital fingerprint code is readable by adigital imaging device, for example to identify the item.

An identification encoder is also called an identification codegenerator or identification code writer.

An identification encoding method, also called identification codewriting method or identification code generating method, is a computerimplemented method that is performed on a hardware (HW) configuration,such as a computer, tablet computer and the like, comprising a centralprocessing unit (CPU), a memory, a storage device such as a hard diskdrive (HDD), a communication interface (IF) device that sends andreceives data to and from other hardware configurations via a network.The hardware configuration may comprise a user interface (UI) devicethat may comprise a display device.

In a preferred embodiment the identification encoder comprises one ormore GPU's for faster writing of a digital fingerprint code in adocument.

In a preferred embodiment, the identification encoder comprises a rasterimage processor to represent the new document of a preferred embodimenton a content output device such as an inkjet printer, and in a morepreferred embodiment, a content output device, such as an inkjetprinter, comprises the identification encoder.

An identification encoder may also be comprised in a desktop publishing(DTP) software package such as Adobe InDesign™, Adobe PageMaker™,QuarkXpress™ or Scribus (http://scribus.net/canvas/Scribus) wherein adigital fingerprint code (DF code) may written in a document that islayouted in the desktop publishing (DTP) software package.

The identification encoding method for a digital fingerprint codecomprises in a preferred embodiment the following steps:

-   -   determining a document; and    -   determining a curve in the document; and    -   determining for an N-bit data of the plurality of N-bit data a        thickness (T_(N,i)) and a length (L_(N,i)); and    -   determining a first segment on the determined curve with        determined length (L_(N,i)); and    -   changing the thickness of the first segment to the determined        thickness (T_(N,i)); and    -   generating from the document with the written digital        fingerprint code a new document.

In a preferred embodiment the new document with the digital fingerprintcode is reproduced by a content output device, such as an inkjetprinter.

The determined curve in a document may for example a segmented outlineof a font from text content in the document. Or it may for example bethe edge of house in an image as content object of the document.

In a preferred embodiment in the identification encoding method the partof the first segment is the whole first segment.

Changing the thickness of the first segment in the identificationencoding method may be at one side of the curve but preferably at bothsides of the curve.

The determined curve in the determined document is preferably determinedby the operator of the identification encoder but more preferablydetermined automatically by interpreting the content objects in thedocument. If a content object is a vector graphic, the interpreting ofthe content object is easily done to determine automatically a curvebecause a vector graphic is defined by curves such as Bezier-curves. Ifthe content object is a raster graphic, the interpreting of the contentobject may be done by image manipulation methods such as edge-detectionmethods.

In a preferred embodiment the changing of the thickness of the segmentcomprises changing the color of the thickness in the color of thedetermined curve.

The changing of the thickness in a segment of a vector-graphic-definedcurve is easily because the segment is also defined as vector graphic.If the segment is of a raster-graphic-defined-curve the thickness of thesegment may be changed by image manipulation methods such as bi-cubicscaling.

An overview of image manipulation methods that may be comprised in theidentification encoder is disclosed in Part 3 “Discrete two-dimensionalprocessing” [Page 145-244] and Part 4 “Image improvement” [Page 245-418]of PRATT, William K. Digital Image Processing: PIKS Scientific Inside.4th edition. John Wiley.

The identification encoder may comprise a data compressor to compressthe plurality of N-bits such as run-length encoding and/or may comprisea data security system wherein the plurality of N-bits is securedencoded by a security key for example a password.

The shape of thickening in the curve of a digital fingerprint code is ina preferred embodiment triangular, quadratic, rectangular, heptagonal,pentagonal, oval, rhombus, octagonal, or elliptical shaped.

In a preferred embodiment the document is a wood pattern, as andecorative pattern and a curve in the set of curves is a nerve or a woodgrain imperfection in the wood pattern:

The identification encoder of a digital fingerprint code (DF-code)comprises in a preferred embodiment the following steps:

-   -   determining a decorative pattern comprising a wood pattern; and    -   determining a nerve or wood grain imperfection in the wood        pattern; and    -   determining for an N-bit data of the plurality of N-bit data a        thickness (T_(N,i)) and a length (L_(N,i)); and    -   determining a first segment on the determined nerve or        determined wood grain imperfections with determined length        (L_(N,i)); and    -   changing the thickness of the segment to the determined        thickness (T_(N,i)); and    -   generating from the wood pattern with the digital fingerprint        code a new wood pattern.

The thickenings on the nerve or the wood-grain imperfection from thedigital fingerprint code (DF code) preferably have the same color as thenerve or the wood-grain imperfection.

The determination of a nerve or wood-grain imperfection in a woodpattern may be performed by image analysis method which may comprisesfast Fourier transformations (FFT), histogram calculations and filteringmethods.

In a preferred embodiment the digital fingerprint code (DF code) is usedto read the content about a decorative workpiece comprising a woodpattern, as decorative pattern, on which the digital fingerprint code isattached.

In another preferred embodiment the digital fingerprint code (DF code)is used to track-and-trace a decorative workpiece comprising a woodpattern, as decorative pattern, on which the digital fingerprint code isattached.

In a preferred embodiment the new wood pattern with the digitalfingerprint code is reproduced by an inkjet printer or gravure printerand in a more preferred embodiment the identification encoder iscomprised in the manufacturing of a decorative workpiece wherein the newwood pattern with the digital fingerprint code, embedded in thedecorative workpiece, is reproduced by an inkjet printer or gravureprinter.

The identification encoding method for a digital fingerprint code may becomprised in the manufacturing of a decorative workpiece.

In another preferred embodiment the identification encoding methoddetermines a curve in a logo which is comprised as content object in thedocument. A logo is a graphic mark or emblem commonly used by commercialenterprises, organizations and even individuals to aid and promoteinstant public recognition. Logos are either purely graphic (symbols /icons) or are composed of the name of the organization (a logotype orwordmark).

In a preferred embodiment a reproduced digital fingerprint code isattached to a security item such as an identity card (IC), a drivinglicense. A preferred embodiment is a security item comprising areproduced digital fingerprint code.

In another preferred embodiment a reproduced digital fingerprint code isattached to a workpiece or package of a workpiece such as a package ofmedicines. This enables the possibilities of track-and-trace a workpieceor the enclosed workpiece in a package or the possibilities of addingsecured information to a workpiece or the package of a workpiece. Adigital fingerprint code may be embedded in the design of the packagewhich makes it difficult to detect and to reproduce by others suppliers.A preferred embodiment is a workpiece such as a decorative workpiece ora package of a workpiece comprising a reproduced digital fingerprintcode.

In another preferred embodiment a reproduced digital fingerprint code isattached to a package of a food such as a package of carrots. Thisenables the possibilities of track-and-trace the enclosed food in apackage, or the possibilities of adding secured information to a packageof a food. A digital fingerprint code may be embedded in the design ofthe package which makes it difficult to detect and to reproduce byothers suppliers, thus against counterfeiting. A preferred embodiment isa food packaging comprising a reproduced digital fingerprint code.

In another preferred embodiment a reproduced digital fingerprint code isattached to a package of application software on a data storage devicesuch as a package of an operating system on a Compact Disc Read-onlymemory (CD-ROM). This enables the possibilities of track-and-traceapplication software or the possibilities of adding secured informationto a package of application software on a data storage device. A digitalfingerprint code may be embedded in the design of the package whichmakes it difficult to detect and to reproduce by others suppliers. Apreferred embodiment is a package of application software on a datastorage device comprising a reproduced digital fingerprint code.

In another preferred embodiment a reproduced digital fingerprint code isattached to a medical device such as a digital radiography panel(DR-panel). This enables the possibilities of track-and-trace themedical device or the possibilities of adding secured information to themedical device. A digital fingerprint code may be attached to themedical device to make it difficult to detect and make it difficult toreproduce the medical device, thus against counterfeiting. A preferredembodiment is a medical device comprising a reproduced digitalfingerprint code.

Another preferred embodiment is a container comprising a liquid whereinthe container comprises a digital fingerprint code.

Identification Decoder

To decode a digital fingerprint code, an identification decoder isneeded for example to identify the item whereon the digital fingerprintcode is attached. An identification decoder is also called anidentification code reader or identification code interpreter.

An identification decoding method, also called an identification codereading method or identification code interpreting method, is a computerimplemented method that is performed on a hardware (HW) configuration,such as a computer, tablet computer and the like, comprising a centralprocessing unit (CPU), a memory, a storage device such as a hard diskdrive (HDD), a communication interface (IF) device that sends andreceives data to and from other hardware configurations via a network.The hardware configuration may comprise a user interface (UI) devicethat may comprise a display device.

In a preferred embodiment the identification decoder comprises one ormore GPU's for faster reading of a captured digital fingerprint code,which is a digital fingerprint code (DF code) on a reproduction of adocument, captured by a digital imaging device.

The identification decoder preferably has a transfer device, such asUSB-cable and USB-connector, and a memory to transfer an image captureddigital fingerprint code from a digital imaging device and to imagemanipulate the image captured digital fingerprint code. More preferablya digital imaging device is comprised in the identification decoder.

The identification decoder for a digital fingerprint code may comprisingthe following steps:

-   -   capturing a digital fingerprint code (DF code) by a digital        imaging device; and    -   determining an image captured curve in the image captured        digital fingerprint code; and    -   determining a set of two-dimensional points (p_(k)) on the image        captured curve a set of thicknesses (t_(k)) of the image        captured curve; and    -   determining the plurality of N-bit data from the set of        thicknesses (t_(k)) and the location of the set of        two-dimensional points (p_(k)) on the image captured curve.

The determination of the image captured curve is performed by a curvesearcher. The determination in a set of two-dimensional points (p_(k))on the image capture curve the set of thicknesses (t_(k)) is performedby a thickness quantifier. The determination the plurality of N-bit datafrom the set of thicknesses (t_(k)) is performed by an interpreter.

Prior the determining the image captured curve in the image captureddigital fingerprint code, the operator of the identification coder mayselect a region of interest of the image captured digital fingerprintcode or may scaling the image captured digital fingerprint code forexample until the borders of the digital fingerprint code in the imagecaptured digital fingerprint code. This enhances the speed of decodingthe digital fingerprint code.

The determination of a image captured curve in an image captured digitalfingerprint code may be performed by image analysis method which maycomprises fast Fourier transformations (FFT), histogram calculations andfiltering methods.

The plurality of N-bit data may be converted to the content (CNT) of thedigital fingerprint code. This step is also called the N-bit datadecoding step of a digital fingerprint code (DF code). The decoding stepis done by a converter.

In a preferred embodiment, the content is analysed after the decodingstep of the digital fingerprint code and comprising the step ofselecting according the analysis an action from a set of actions. Anaction may for example be opening a web-page with as address the content(CNT) in the image captured digital fingerprint code.

In another preferred embodiment, the plurality of N-bit data is analysedand comprising the step of selecting according the analysis an actionfrom a set of actions.

The distances between two succeeding two-dimensional points (p_(k)) onthe image captured curve is preferably smaller than 10 times the minimumpixel width or height of the captured digital fingerprint code and morepreferable smaller than 5 times, most preferable smaller than 2 times,the minimum pixel width or height of the captured digital fingerprintcode, because this guarantees a better sampling of the image capturedcurve from the digital fingerprint code so the generation of aone-dimensional signal and the determination of the plurality of N-bitsfrom the identification code, embedded in the digital fingerprint code,is easier.

In the decoding step the plurality of N-bit data may be decompressedand/or decrypted and/or error corrected to convert the plurality ofN-bit data to the content (CNT) of the digital fingerprint code. Theerror correcting of the plurality of N-bit data is preferably based onerror-coding code comprised in the plurality of N-bit data.

In a preferred embodiment the image captured curve is approximated by apath (P) which comprises a plurality of two-dimensional points (p_(k));and wherein in the set of two-dimensional points (p_(k)) a set ofthicknesses (t_(k)) is determined.

Another preferred embodiment may comprise the step:

-   -   approximating the skeleton (S) of the image captured curve in        the image captured digital fingerprint code which comprises a        plurality of two-dimensional points (p_(k)). The skeleton (S)        may be converted to a path (P) to approximate the image captured        curve.

To determining the set of two-dimensional points (p_(k)) on the imagecaptured curve easily the curves in the set of curves in the digitalfingerprint code, the curves may not intersects with each other and/ormay not intersects with themselves. A curve in a preferred embodiment isin a preferred embodiment a non-self-intersecting curve.

A skeleton of an image captured curve is a thin version of that shapethat is equidistant to its boundaries of the image captured curve. Theskeleton usually emphasizes geometrical and topological properties ofthe image captured curve, such as its connectivity, topology, length,direction, and width. It serves as a representation of the imagecaptured curve.

Methods to determine a skeleton are disclosed in chapter 5 of J. R.PARKER. Algorithms for image processing and computer vision. John Wiley.ISBN 0471140562.

The conversion of a skeleton (S) of the image captured curve to a path(P) in a preferred embodiment is done by tracing methods, also calledvectorization methods. The tracing method preferably comprising an edgedetection algorithm.

For a fast reading of captured digital fingerprint code the skeleton ofthe image captured curve is determined by a distance skeleton algorithmsuch as Zhang-Suen parallel thinning method which is disclosed at T. Y.ZHANG AND C. Y. SUEN. A fast parallel algorithm for thinning digitalpatterns. Communications of the ACM. 1984, vol. 27, no. 3, p. 236-239.

Prior the step of determining the image captured curve the imagecaptured digital fingerprint code may be converted to an indexed colorimage and more preferably to a binary image. The conversion to anindexed color makes it easier to detect the image captured curve byimage manipulation methods such as edge detection.

Captured digital fingerprint codes may be captured with for exampledifferent illumination conditions for the same digital fingerprint code.Also for example the different resolutions of digital imaging devices,the angles wherein the digital fingerprint code is taken may givedifferent algorithm to make identification readable for a set of digitalimaging devices. That's why in a preferred embodiment the image captureddigital fingerprint code is converted to an indexed color image such asa binary image so the determination of the image captured curve iseasier and the determination of the plurality of N-bit data is fasterdetermined.

The image captured curve and/or image captured digital fingerprint codemay be morphed by morphological image methods such as dilatation,scaling, rotating, translating, warping to enhance fast determination ofan image captured curve of the digital fingerprint code.

Methods of morphology in images are disclosed J. R. PARKER. Algorithmsfor image processing and computer vision. John Wiley. ISBN 0471140562.And especially in chapter 2 and 3.

By following the trace of the image captured curve or the skeleton (S)or the path (P), the thicknesses and the length of the thicknesses inthe image captured curve is determined in a plurality of points. Thesedeterminations are in a preferred embodiment of the identificationdecoder to a plurality of N-bit data.

If for each value of N-bit data in a preferred embodiment has a color(C_(N,i)), tracing of the image captured curve or the skeleton (S) orthe path (P), the thickness and the length of the thicknesses and thecolor of the thicknesses is determined in a plurality of points.

In a preferred embodiment the digital fingerprint code is embedded in anerve or wood grain imperfection of a decorative pattern comprised in adecorative workpiece, such as a decorative panel, comprising a woodpattern as decorative pattern. Thus in a preferred embodiment theidentification decoding method comprises the following step:

-   -   capturing the decorative pattern in a decorative workpiece; and    -   determining an image captured nerve or image captured wood grain        imperfection in the image captured decorative pattern; and    -   determining a set of two-dimensional points (p_(k)) on the image        captured nerve a set of thicknesses (t_(k)) of the image        captured nerve; and    -   determining the plurality of N-bit data from the set of        thicknesses (t_(k)) and the location of the set of        two-dimensional points (p_(k)) on the image captured nerve or        the image capture wood grain imperfection.

Instead of a nerve, the curve may be any wood grain imperfections, suchas knots, cracks in the wood pattern.

A nerve is a wood grain line in the wood pattern which is caused bygrowth rings, especially smaller growth rings, in wood.

Digital Fingerprint Code

A digital fingerprint code (DF code) is an optical-machine-readablereproduction of content (CNT). The digital fingerprint code in apreferred embodiment is readable by a digital imaging device.

The digital fingerprint code in a preferred embodiment is embedding aplurality of N-bit data to represent a content (CNT). The value of anN-bit data is selected from 0 to (2^(N)−1) and hence there are two tothe power of N possible values. N is a positive natural number and N islarger than zero.

The content may comprise a serial number, a code name, a date, such asthe date of reproducing, of an item whereon the digital fingerprint codeis attached. The content may comprise the reproduction characteristicsof the reproducing of the digital fingerprint code.

The plurality of N-bit data is preferably a plurality of hexadecimalnumbers (N=4), more preferably a plurality of octal numbers (N=3) andmost preferably a plurality of binary data (N=1), also called a bitstream.

Larger the amount of possible values in an N-bit data of the preferredembodiment, higher the amount of storage capacity of the digitalfingerprint code.

The storage capacity defines the maximum amount of bits that a digitalfingerprint code (DF code) embeds a plurality of N-bit data. The storagecapacity is sometimes defined by the maximum amount of bytes that adigital fingerprint code (DF code) embeds a plurality of N-bit data.

Larger the total length of the set of curves in the preferredembodiment, higher the amount of storage capacity of the digitalfingerprint code on the set of curves.

In a preferred embodiment the storage capacity of the digitalfingerprint code on the set of curves is between 1 bit and 10 bits permillimetre, more preferably between 1 bit and 20 bits per millimetre andmost preferably between 1 bit and 50 bits per millimetre.

Smaller the minimal thickness (T_(N,i)) and smaller the minimal length(L_(N,i)) of a value from an N-bit data, for example by a larger outputresolution of an content output device, larger the storage capacity ofthe digital fingerprint code.

In a preferred embodiment a digital fingerprint code (DF code) isvisible by only using human eyes at a viewing distance between 0millimetres and 200 millimetres, more preferably between 0 decimetre and50 millimetres and most preferably between 0 decimetre and 10millimetres.

The plurality of N-bit data may comprise a header sequence of pluralityof N-bit data to identify easier the start of the plurality of N-bitdata and/or a tail sequence of plurality of N-bit data to identifyeasier the tail of the plurality of N-bit data. Preferably the headersequence and/or tail sequence have a fixed size.

The plurality of N-bit data may comprise an order sequence of aplurality of N-bit data to identify the order of the curve in the set ofcurves from the preferred embodiment. This order sequence is used toordering the set of plurality of N-bit data from each curve and toconcatenate them in the correct order to one set of plurality of N-bitdata.

The plurality of N-bit data may comprise an error-correcting code. Theerror-correcting code may comprise parity checks and/or check sums toimprove the error-correcting code.

An error-correcting code is to achieve error detection and correction byadding redundancy, for example by adding extra to an content (CNT),which identification decoders can use to check consistency of thecontent (CNT), and to recover data determined to be corrupted. In apreferred embodiment the plurality of N-bit data comprises a Hammingcode as error-correcting code. An example of a high speed Hamming codecircuit is disclosed in U.S. Pat. No. 4,276,647 (XEROX CORPORATION).

An error correction capability in a digital fingerprint code (DF code)has advantage if the reproduction of a digital fingerprint code (DFcode) in a preferred embodiment is dirty or damaged.

The plurality of N-bit data may comprise a compressed plurality of N-bitdata, compressed by a data compression method such asrun-length-encoding method. Preferably the compressed N-bit data iscompressed by a lossless data compression method. Lossless datacompression methods exploit statistical redundancy to represent datamore concisely without losing information, so that the process isreversible by decompression.

The digital fingerprint code in a preferred embodiment comprises a setof curves wherein an content (CNT) is embedded by a plurality of N-bitdata;

-   wherein each possible value of N-bit data has a thickness (T_(N,i))    and length (L_(N,i)); and-   wherein the plurality of N-bit data comprises a first N-bit data    (N₁), subsequent by a different second N-bit data (N₂) on a curve of    the set of curves; and-   wherein the thickness (T_(N,i,1)) of the value (v_(N,1)) of the    first N-bit data (N₁) on the curve is different from the thickness    (T_(N,i,2)) of the value (v_(N,2)) of the second N-bit data (N₂)    and/or wherein the length of the value (v_(N,1)) of the first N-bit    data (N₁) on the curve is different from the length (L_(N,i,2)) of    the value (v_(N,2)) of the second N-bit data (N₂).

In a preferred embodiment the plurality of N-bit data comprises morethan two N-bit data's.

For the sake of clarity, it should be clear that a curve is atwo-dimensional continuous line which doesn't have to be straight. Acurve has a start point and an end point. The start point and the endpoint may be the same such as a circular curve. The length of the curveis preferably finite and bounded. In a preferred embodiment the digitalfingerprint code comprises a set of non-self-intersecting-curves whereina content (CNT) is embedded by a plurality of N-bit data with more thantwo N-bit data's. A curve in a preferred embodiment is continue anduninterrupted.

The thickness (T_(N,i)) and length (L_(N,i)) for each possible value ofN-bit data gives the possibilities to get an one-to-one relation betweenthickness-and-length and a value of an N-bit-data.

The thickness (T_(N,i)) is preferably between 0.002 mm and 5 mm and morepreferably between 0.005 mm and 5 mm and most preferably between 0.005mm and 2 mm.

The length (L_(N,i)) is preferably between 0.002 mm and 5 mm and morepreferably between 0.005 mm and 5 mm and most preferably between 0.005mm and 2 mm.

The minimal thickness (T_(N,i)) and minimal length (L_(N,i)) depends onthe true output resolution of the content output device and the qualityof the reproduction of the digital fingerprint code (DF code).

As example of a preferred embodiment a 100% black digital finger printcode is printed at 4000 dpi with an offset printing device. One pixel isminimal 0.00635 millimetre (mm) but to detect the thicknesses on thecurve by a preferred identification decoding method the thickness theminimal thicknesses is 4 pixels, which is 0.0254 millimetre, and morepreferably 16 pixels, which is 0.1016 millimetre.

Assuming the digital finger print code is printed at 10160 dpi with anoffset printing device. One pixel is minimal 0.0025 mm but to detect thethicknesses on the curve by a preferred identification decoding methodthe minimal thicknesses is 4 pixels, which is 0.01 mm, and morepreferably 16 pixels, which is 0.04 mm.

In a preferred embodiment the minimal thickness for a value of an N-bitin the digital fingerprint code is between 2 and 100 pixels, morepreferably between 4 and 50 pixels and most preferably between 8 and 25pixels. Larger the minimal thickness, lower the print quality of theprinted digital fingerprint have to be but more noticeable thereproduced digital fingerprint code is by the human eye.

In a preferred embodiment the minimal length for a value of an N-bit inthe digital fingerprint code is between 2 and 100 pixels, morepreferably between 4 and 50 pixels and most preferably between 8 and 25pixels. Larger the minimal thickness, lower the print quality of theprinted digital fingerprint have to be but more noticeable thereproduced digital fingerprint code is by the human eye.

In a preferred embodiment the digital fingerprint code has for eachvalue of N-bit data a color (C_(N,i)); and the color (C_(N,i,1)) of thevalue (v_(N,1)) of the first N-bit data (N₁) on the curve is differentfrom the color (C_(N,i,2)) of the value (v_(N,2)) of the second N-bitdata (N₂).

The digital fingerprint code with for each value of N-bit data a color(C_(N,i)) may only use a specific amount of colors. The color (C_(N,i))may be selected from a set of colors.

The thickness (T_(N,i)), length (L_(N,i)) and color (C_(N,i)) for eachpossible value of N-bit data gives the possibilities to get anone-to-one relation between a value of an N-bit-data andthickness-and-length-and-color.

If in the digital fingerprint code the amount of the curves in the setof curves is more than one, the digital fingerprint code may compriseanother curve wherein a binary code is embedded with a plurality ofM-bit data with more than two M-bit data's; and wherein M is differentto N; and wherein each possible value of M-bit data has a thickness(T_(M,j)) and length (L_(M,j)) a curve; and

-   wherein the plurality of M-bit data comprises a first M-bit data    (M₁), subsequent by a different second M-bit data (M₂); and wherein    the thickness (T_(M,j,1)) of the value (v_(M,1)) of the first M-bit    data (m₁) on the another curve is different from the thickness    (T_(M,j,2)) of the value (v_(M,2)) of the second M-bit data (M₂)    and/or wherein the length (L_(M,j,1)) of the value (v_(M,1)) of the    first M-bit data (M₁) on the another curve is different from the    length (L_(M,j,2)) of the value (v_(M,2)) of the second N-bit data    (M₂).

The digital fingerprint code is in a preferred embodiment comprised in adocument and in a more preferred embodiment comprised in a contentobject of a document.

The digital fingerprint code is preferably a raster graphic and morepreferably a vector graphic. The digital fingerprint code may comprise aplurality of raster graphics and/or a plurality of vector graphics. Forexample the curve is raster graphic and the thicknesses on the curvewhich represents the plurality of the N-bit data may be a plurality ofvector graphics.

In a preferred embodiment the plurality of N-bit data is an unipolarline code. It is the simplest line code, directly encoding the bitstream, and is analogous to on-off keying in modulation.

Digital Imaging Devices

A digital imaging device captures an image, for example for a reproduceddocument, and generates a color signal from the image to an outputdevice having specific color sensitivities, the digital imaging devicefurther being one of many devices of the same type useful with theoutput device. The digital imaging device, for example a digital camera,includes a color sensor for capturing the image and generating a colorsignal from the captured image, the color sensor having predeterminedspectral sensitivities, and an optical section that is interposed in theimage light directed to the color sensor, the optical section alsohaving predetermined spectral characteristics. The combination of thespectral sensitivities of the color sensor and the spectralcharacteristics of the optical section uniquely distinguish thisparticular digital imaging device from other digital imaging devices ofthe same type.

In a preferred embodiment the digital imaging device comprises acharge-coupled device (CCD) camera, which is a digital video camera thatfeeds its image in real time to a computer or computer network such asan IP camera (which uses a direct connection using ethernet or Wi-Fi) ora webcam connected by a USB cable, FireWire cable or similar cable. Sucha web-cam is preferably comprised in a mobile phone or mobile computersuch as a tablet computer.

In another preferred embodiment the digital imaging device is a digitalmicroscope which comprises a charge-coupled device (CCD) camera thatfeeds its image in real time to a computer or computer network after theimage is magnified more than eight times, preferably more than 30 times,by an optical system. The maximum magnification of the digitalmicroscope is preferably larger than 30 times, more preferably largerthan 50 times and most preferably larger than 100 times. If the digitalfingerprint code is small, the reproduced digital fingerprint code haveto be captured via an optical system by a digital imaging device, elsethe identifying decoder may not read the plurality of N-bit data,embedded in the digital fingerprint code.

A digital imaging device may comprise a complementarymetal-oxide-semiconductor (CMOS) sensor.

Preferably the digital imaging device comprises an illumination device,such as a light-emitting-diode (LED) flash, to capture the digitalfingerprint code of a preferred embodiment by the light of theillumination device in darker situations.

To enhance the storage capacity of the digital fingerprint code on theset of curves the resolution of the digital imaging device is preferablymore than 5 megapixels (MPx). One megapixel (MPx) is one million pixels,and is a term used not only for the number of pixels in an image, butalso to express the number of image sensor elements of digital imagingdevices or the number of display elements of display devices. Forexample the mobile phone iPhone™ 4 features a backside-illuminated 5megapixel rear-facing camera with a 3.85 mm f/2.8 lens.

The resolution of a digital imaging device is preferably more than 8megapixels and more preferably more than 12 megapixels.

The digital imaging device is preferably a three color digital camera,such as an RGB digital camera.

The digital imaging device may comprise an image manipulation device tomanipulating a captured image, such as a captured digital fingerprintcode prior to transfer it to an identification decoder. The imagemanipulation device of the digital imaging device may comprise one ormore GPU' s for faster manipulating the captured image, such as acaptured digital fingerprint code. An example of manipulating a capturedimage in a digital imaging device is color conversion (CMS) to anindependent color space, such as CIE Lab or to a dependent colorantspace, such as sRGB as specified in IEC 61966-2-1:1999. Another digitalexample of manipulating a captured image in a digital imaging device isdigital magnifying the captured image by a determined magnifier.

The digital imaging device may comprise an image manipulation devicewhich performs an image processing method selected from: color and/orcolorant space converting (CMS); auto-contrasting; unsharp masking(USM); content object location correcting; noise reducing; despeckling;applying a convolution; rotating; scaling; cropping; despeckle; destair;casting.

Content Output Devices

More and more content output devices, such as display devices, projectordevices and printer devices, are developed for the reproduction ofcontent such as images and text. Examples of content output devices thatare used to reproduce a document are CRT's, LCD's, plasma display panels(PDP), electroluminescent displays (ELD), carbon nanotubes, quantum dotdisplays, laser TV's, Electronic paper, E ink, projection displays,conventional photography, electrophotography, dot matrix printers,thermal transfer printers, dye sublimation printers and inkjet systemsto name a few. Also the conventional printing systems such as offsetprinting, lithography, rotogravure, flexography, letterpress printing,and screen-printing are developed for the reproduction of images and/ortext and are thus also content output devices.

An apparent output resolution of a content output device refers to thefact that the human eye perceives an image as having greater detail thanit does in physical reality, which is defined by the true outputresolution. The apparent and the true output resolutions are defined indots per inch (dpi), especially for printer devices and defined inpixels per inch (ppi), especially for display devices and also calledpixel density. One inch is exactly 25.4 millimetre.

In a preferred embodiment the digital fingerprint code is reproduced acontent output device with a true output resolution more than 300 dotsper inch or 300 pixels per inch and in a more preferred embodiment thedigital fingerprint code is reproduced by a content output device with atrue output resolution more than 2400 dots per inch (dpi) and in a mostpreferred embodiment the digital fingerprint code is reproduced by acontent output device with a true output resolution more than 4800 dotsper inch (dpi).

Larger the true output resolution and the apparent output resolution ofa content output device, smaller a digital fingerprint code (DF code)and/or smaller the thickness differences (T_(N,i)) and smaller thelength differences (L_(N,i)) in a digital fingerprint code (DF code) maybe reproduced.

Smaller digital fingerprint codes and/or smaller thickness differencesand/or length differences in a digital fingerprint code (DF code) makesit for example possible to write and to reproduce digital fingerprintcodes that are not visible by the human eye at an distance of more than20 centimetre, which is a normal reading distance.

Rotogravure (roto or gravure for short) is a type of intaglio printingprocess, which involves engraving the image onto an image carrier. Ingravure printing, the image is engraved onto a cylinder because, likeoffset printing and flexography, it uses a rotary printing press.Rotogravure process by a gravure printer is still used for commercialprinting of magazines, postcards, and corrugated (cardboard) productpackaging and the manufacturing of decorative workpieces.

Offset printing, which is an example of a conventional printing system,is a printing technique in which ink is spread on a metal plate withetched images, then transferred (offset) to an intermediary rubberblanket and finally to the printing surface by pressing the paper to theblanket. When printing color images, four plates are normally used, onefor each CMYK component. Additionally, spot colors can be added byadding a new layer with the specific pigment needed.

Nowadays modern offset systems use computer to plate technology, whichcreate plates directly from the computer output, contrary to the oldertechnology where photographic films were created by computers and thenused for creating the plate. Offset presses are big, expensive andcomplex devices which require experienced operators to run them. Theprocess of preparing a document to be printed in an offset press iscomplicated, since plates have to be created and the operators have tospend some time manually preparing and calibrating the offset press toget the desired result. Even though this process is rather expensive andslow, the actual printing process is cheap, fast and produces high imagequality. This makes it a good solution for producing large amounts ofcopies. For this reason, it has become the most popular way ofcommercial printing and it is largely used for printing newspapers,magazines, books, etc.

In an inkjet system, which is an example of a digital printing system,the ink is directly deposited, also called jetted, onto a substrate,simplifying the printing mechanism and eliminating all the process ofcreating plates. Besides, it avoids the extra job that offset operatorsneed to do in order to get the offset press ready for printing. Boththings lead to a shorter turnaround time, cheaper starting point for asingle copy and copies customization which is not possible in offsetsince it is unviable to create a different plate for each copy.

Another advantage is the possibility of print a wider gamut (closer tothe RGB gamut) than with offset. Also it is easier to print in almostevery surface: wood, ceramic, plastic, etc. The quality of offsetpresses has always been considered higher in terms of resolution andcrispness than for digital presses such as inkjet systems, althoughnowadays there are digital presses such as inkjet systems matching upthe quality of offset presses. Nevertheless, digital printing has somedisadvantages with respect to offset which can make difficult thedecision of choosing one or another printing method. The resolution of adigital press depends on the dots per inch (dpi) parameter. Even thoughthis parameter has been gradually increasing over the years, the qualityof a digital press cannot be compared yet to the quality of an offsetpress in terms of resolution and crispness. Another shortcoming ofdigital presses is the handling of spot colors. Typically a digitalpress uses CMYK pigments to represent all the colors. As mentioned, onlya subset of spot colors can be properly reproduced using CMYK.

Some complex digital presses use an additional fifth or sixth colorantwhich helps to the reproduction of a larger subset of spot colors butstill not enough to reproduce all of them in a good way.

Preferably the digital fingerprint code is reproduced by offset printingand more preferably the digital fingerprint code of a preferredembodiment is reproduced by inkjet printing.

In another preferred embodiment the digital fingerprint code isreproduced by a micro-lithography device or by a nano-lithographydevice. Micro-lithography and nano-lithography refer specifically tolithographic patterning methods capable of structuring material on afine scale. Typically, features smaller than 10 micrometers areconsidered micro-lithographic, and features smaller than 100 nanometersare considered nano-lithographic. Photolithography is one of these twomethods, micro- and nano-lithography, often applied to semiconductormanufacturing of microchips. Photolithography is also commonly used forfabricating Microelectromechanical systems (MEMS) devices.Photolithography generally uses a pre-fabricated photomask or reticle asa master from which the final pattern is derived. Althoughphotolithographic technology is the most commercially advanced form ofnanolithography, other techniques are also used for example electronbeam lithography is capable of much true output resolutions (sometimesas small as a few nanometers).

Graphic Processing Units

Graphic Processing Units (GPU's) have been used to render computergraphics for years. Nowadays they are also used for general-purposetasks due to their highly parallel structure, making them more efficientthan Central Processing Units (CPU's).

GPU's can be combined with CPU's to achieve greater performance. In thisway, serial parts of the code would run on the CPU and parallel partswould do it on the GPU. While CPU's with multiple cores are availablefor every new computer and allow the use of parallel computing, theseare focused on having a few high performance cores. On the other hand,GPU's have an architecture consisting of thousands of lower performancecores making them especially useful when large amount of data have to beprocessed.

One of the most popular tools available on the market of GPU computingis CUDA. CUDA is a parallel computing platform and programming modelcreated by Nvidia™ and available only for their GPU's. The mainadvantage of CUDA is its ease of use, using the language known as CUDA Cwhich is essentially an extension of C, with similar syntax and veryeasy to integrate in a C/C++ environment.

The needed data is first copied from the main memory to the GPU memory({circumflex over (1)}), the CPU sends an instruction to the GPU({circumflex over (2)}), the GPU executes the instruction in all theparallel cores at the same time ({circumflex over (3)}), and the resultis copied back from the GPU memory to the main memory ({circumflex over(4)}).

CUDA parallel execution units consist of threads grouped into blocks.Combining the use of blocks and threads the maximum number of availableparallel units can be launched, which for the latest GPU's can be morethan 50 million. Even though this is a great amount of parallelcapability, there are some cases where data might exceed the limit. Inthose cases, the only possibility is to iterate through the grid ofmillions of parallel units as many times as needed till all the data isprocessed.

Path

A path in a preferred embodiment is defined as a sequence of minimal twotwo-dimensional points, also called 2D-points, which are connected witha sub-path. A sub-path may be a curve defined as a 2D-function between2D-points such as a line, polygon, a Bezier curve or a parametricequation. It is not necessary that each sub-path is using the same2D-function. A 2D-point is defined as a point with an x-coordinate andy-coordinate as used in a Cartesian coordinate system. A 2D-point of apath may be referred as a point.

Decorative Image

A decorative image is an image representing wood, stone, rock or fantasypattern.

A decorative image is achieved by suitable commercially availablehardware, such as scanning a photograph or taking an image by a digitalcamera, and commercially available software, such as Adobe Photoshop™ tomanipulate and create decorative images.

The content of a decorative image is preferable defined in rastergraphics format such as Portable Network Graphics (PNG), Tagged ImageFile Format (TIFF), Adobe Photoshop Document (PSD) or Joint PhotographicExperts Group (JPEG) or bitmap (BMP) but more preferably in vectorgraphics format, wherein the decorative image as raster graphics formatis embedded. Preferred vector graphics formats are Scale Vector Graphics(SVG) and AutoCad Drawing Exchange Format (DXF) and most preferably thedecorative image is embedded in a page description language (PDL) suchas Postscript (PS) or Portable Document Format (PDF).

A decorative image may be stored and/or loaded as one or more files on amemory of a computer. A preferred embodiment may comprise a method toload a decorative image into a memory of a computer.

Decorative Patterns

The decorative pattern is a region-of-interest from a decorative imageso variances in decorative patterns may be achieved by selectingdifferent region-of-interests in the decorative image. The ratio of thearea of such a region-of-interest as decorative pattern and the area ofthe decorative image is preferably between 50% and 100%, more preferablybetween 10% and 100% and most preferably between 1% and 100%. The areawith the content of the region-of-interest as decorative pattern is alsocalled content area. The size of the region-of-interest and thus thedecorative pattern may have a width between 50 mm and 4000 mm, and alength between 100 mm and 6000 mm or more.

A decorative pattern is preferable rectangular shaped but it can also betriangular, quadratic, rectangular, heptagonal, pentagonal andoctagonal, or elliptical shaped. A decorative pattern may have a sidewith 1 or more curved parts. The advantage of rectangular shapeddecorative patterns is the ease of cutting to a decorative workpiece.Rectangular or non-rectangular shaped decorative patterns may be cut bycutting plotters. The use of cutting plotters is more time-consuming butnon-rectangular shaped decorative patterns expand the amount ofassembling creations of decorative workpieces such as mosaic flooringwith laminates, or design furniture.

The content of a decorative pattern is preferable defined in rastergraphics format such as Portable Network Graphics (PNG), Tagged ImageFile Format (TIFF), Adobe Photoshop Document (PSD) or Joint PhotographicExperts Group (JPEG) or bitmap (BMP) but more preferably in vectorgraphics format, wherein the decorative pattern as raster graphicsformat is embedded. Preferred vector graphics formats are Scale VectorGraphics (SVG) and AutoCad Drawing Exchange Format (DXF) and mostpreferably the decorative pattern is embedded in a page descriptionlanguage (PDL) such as Postscript (PS) or Portable Document Format(PDF).

A decorative pattern may be stored and/or loaded as one or more files ona memory of a computer. A preferred embodiment may comprise a method toload a decorative pattern to a memory of a computer.

Decorative Workpiece

The decorative workpieces are preferably rigid or flexible panels, butmay also be rolls of a flexible substrate. In a preferred embodiment thedecorative workpieces are selected from the group consisting of kitchenpanels, flooring panels, furniture panels, ceiling panels and wallpanels.

In a more preferred embodiment, the decorative workpiece includes atongue and a groove capable of achieving glue less mechanical join.

The decorative workpieces, especially decorative panels, may furtherinclude a sound-absorbing layer as disclosed by U.S. Pat. No. 8,196,366(UNILIN).

In a preferred embodiment, the decorative panel is an antistatic layeredpanel. Techniques to render decorative panels antistatic are well-knownin the art of decorative workpieces as exemplified by EP1567334(FLOORING IND).

In a preferred embodiment, the decorative panels are made in the form ofrectangular oblong strips. The dimensions thereof may vary greatly.Preferably the panels have a length exceeding 1 meter, and a widthexceeding 0.1 meter, for example the panels can be about 1.3 meter longand about 0.15 meter wide. According to a special preferred embodimentthe length of the panels exceeds 2 meter, with the width beingpreferably about 0.2 meter or more. The decorative pattern of suchpanels is preferably free form repetitions.

Core Layers

The core layer is preferably made of wood-based materials, such asparticle board, MDF or HDF (Medium Density Fibreboard or High DensityFibreboard), Oriented Strand Board (OSB) or the like. Also, use can bemade of boards of synthetic material or boards hardened by means ofwater, such as cement boards. In a particularly preferred embodiment,the core layer is a MDF or HDF board.

The core layer may also be assembled at least from a plurality of papersheets, or other carrier sheets, impregnated with a thermosetting resinas disclosed by WO 2013/050910 (UNILIN). Preferred paper sheets includeso-called Kraft paper obtained by a chemical pulping process also knownas the Kraft process, for example as described in U.S. Pat. No.4,952,277 (BET PAPERCHEM)

In another preferred embodiment, the core layer is a board materialcomposed substantially of wood fibres which are bonded by means of apoly-condensation glue, wherein the poly-condensation glue forms 5 to 20percent by weight of the board material and the wood fibres are obtainedfor at least 40 percent by weight from recycled wood. Suitable examplesare disclosed by EP2374588 (UNILIN).

Instead of a wood based core layer, also a synthetic core layer may beused, such as those disclosed by US2013062006 (FLOORING IND). In apreferred embodiment, the core layer comprises a foamed syntheticmaterial, such as foamed polyethylene or foamed polyvinyl chloride.

Other preferred core layers and their manufacturing are disclosed byUS2011311806 (UNILIN) and U.S. Pat. No. 6,773,799 (DECORATIVE SURFACES).

The thickness of the core layer is preferably between 2 and 12 mm, morepreferably between 5 and 10 mm.

Tongue-and-Groove Profile

The side edge of a decorative workpiece of the set of separatedecorative workpiece may be milled to produce a tongue or a grooveprofile, to make it possible to interconnect decorative workpieces, alsoclick decorative workpieces, such as click laminates. The advantagethereof is an easy assembly requiring no glue. The shape of the tongueand groove profile necessary for obtaining a good mechanical join iswell-known in the art of laminate flooring, as also exemplified in EP2280130 A (FLOORING IND), WO 2004/053258 (FLOORING IND), US 2008010937(VALINGE) and U.S. Pat. No. 6,418,683 (PERSTORP FLOORING).

Methods for Manufacturing Decorative Workpieces

The method for manufacturing decorative workpieces according to apreferred embodiment may comprise the steps:

-   -   gravure printing the decorative pattern; and    -   impregnating a paper substrate with a thermosetting resin; and    -   heat pressing the thermosetting resin impregnated paper        substrate carrying the inkjet printed decorative pattern into a        decorative workpiece.

The method for manufacturing decorative workpieces according to apreferred embodiment may comprise the steps of:

-   -   inkjet printing a decorative pattern, preferably with one or        more aqueous inkjet inks on a paper substrate; and    -   impregnating a paper substrate with a thermosetting resin; and    -   heat pressing the thermosetting resin impregnated paper        substrate carrying the inkjet printed decorative pattern into a        decorative workpiece.

In a preferred embodiment, the method for manufacturing decorativeworkpieces comprises, in order, the steps of:

-   a) inkjet printing a decorative pattern with one or more aqueous    inkjet inks on a paper substrate; and-   b) impregnating the inkjet printed paper substrate with a    thermosetting resin; and-   c) heat pressing the thermosetting resin impregnated paper substrate    carrying the inkjet printed decorative pattern into a decorative    workpiece.

In another preferred embodiment, the method for manufacturing decorativeworkpieces includes, in order, the steps of:

-   a) impregnating a paper substrate with a thermosetting resin;-   b) inkjet printing a decorative pattern with one or more aqueous    inkjet inks on the thermosetting resin impregnated paper; and-   c) heat pressing the thermosetting paper carrying the inkjet printed    decorative pattern into a decorative workpiece. In the latter,    financial losses due to cutting errors are minimized.

The thermosetting resin impregnated paper carrying the inkjet printeddecorative pattern is heat pressed between a protective layer containinga thermosetting resin and a core layer, with the decorative patternfacing the protective layer. In the latter, the thermosetting resinimpregnated paper preferably includes a whitening agent for maskingsurface defects of the core layer.

Alternatively the thermosetting resin impregnated paper carrying thedecorative pattern is heat pressed as a protective layer into adecorative workpiece, with the decorative pattern facing towards a corelayer present in the decorative workpiece. The protective layer (oroverlay) contains no or substantially no whitening agent because theoverlay becomes transparent after heat pressing so that the decorativepattern can be viewed. The decorative pattern must face the core layerbecause otherwise the decorative pattern would rapidly deterioratethrough wear. In a further preferred embodiment the decorative patternincludes as outermost ink layer a white ink layer. The outermost whiteink layer means that the decorative pattern inkjet printed on theoverlay covered by a white ink layer, preferably applied by inkjetprinting, but e.g. screen printing or flexographic printing is alsopossible. By having an outermost white ink layer on the decorativepattern, the paper layer between the core layer and the overlay can beomitted, which represents not only a cost benefit but also a simplifiedmanufacturing process.

In a preferred embodiment of the manufacturing method, the thermosettingresin impregnated paper includes a coloured paper substrate, morepreferably a bulk coloured paper substrate. The use of a coloured papersubstrate reduces the amount of inkjet ink required to form thedecorative pattern.

In a preferred embodiment of the manufacturing method, the colouredpaper substrate is prepared by impregnating the paper substrate with acoloured thermosetting resin.

In a preferred embodiment of the manufacturing method, the protectivelayer includes hard particles in an amount between 1 g/m² and 100 g/m².

In a preferred embodiment of the manufacturing method, the thermosettingresin is a melamine based resin. A melamine based resin is preferred notonly because of its excellent physical properties against wear, but alsobecause of the clear transparency after heat pressing showing nodiscolouration.

In a preferred embodiment of the manufacturing method, the protectivelayer includes hard particles in an amount between 1 g/m² and 100 g/m².

In a preferred embodiment, the method of manufacturing a decorativeworkpiece comprises the step of hot pressing at least the core layer andthe decorative layer which includes a decorative pattern and athermosetting resin provided paper. Preferably the method of theinvention forms part of a DPL (Direct Pressure Laminate) process asabove described, wherein the decorative layer is taken up in a stack tobe pressed with the core layer and a balancing layer, and preferablyalso a protective layer. It is of course not excluded that the method ofthe invention would form part of a CPL (Compact Laminate) or an HPL(High Pressure Laminate) process in which the decorative layer is hotpressed at least with a plurality of resin impregnated core paperlayers, e.g. of so called Kraft paper, forming a substrate underneaththe decorative layer, and wherein the obtained pressed and curedlaminate layer, or laminate board is, in the case of an HPL, glued to afurther substrate, such as to a particle board or an MDF or HDF board.

In a preferred embodiment, a protective layer containing a thermosettingresin is applied onto the inkjet printed decorative pattern, wherein thethermosetting resin may be a colored thermosetting resin to reduce theamount of inkjet ink to be printed.

In a preferred embodiment of the manufacturing method, the inkjetprinting is performed by a single pass printing inkjet printing process.This allows for a high productivity (m² decorative workpiece per hour).Alternatively a plurality of multipass inkjet printers is used.

EXAMPLES

An example of an identification encoding method for digital fingerprintcodes is described and an example of an identification decoding methodfor digital fingerprint codes is described.

Example of an Identification Encoding Method

An example of a preferred embodiment is detailed as followed:

In this example the focus of the content is a string message, but sinceall data can be represented by bits, most of the methods in this sectionare independent of the kind of data. The string message is converted toa plurality of binary data.

Representing Bits by Line Thickness

The first step in encoding any kind of data is choosing in the example away to represent a value ‘1’ and a value ‘0’ with the given medium. Thegiven medium is, in this case, is the thickness of the line. Threepossibilities are explored:

a) The first way of representing bits is as a piece of line of fixedlength, separated by a shorter piece of line, with three differentlevels of thickness: the smallest for the transition between two bits,the thickest for a one, and the one in between for a zero. This way ofrepresenting bits is shown as a signal in FIG. 1.

b) The second way of representing bits is using only two levels. Onelevel to signal a change of the ‘current’ bit, and a second to decidehow much times that bit was present, by making it longer for more bits.To make it more clear, this way of representing bits is shown as asignal in FIG. 2.

The two previous ways of representing bits both have advantages anddisadvantages.

The first way has a fixed length between the start of every bit, and asignal change at those locations. This makes it easier to detect bits,as the identification decoding method knows it has to find a signalchange at regular intervals. It also can detect missed bits because of atoo large distance between two successive bits. When a distance is toolarge, the identification decoding method can start looking for a signalchange somewhere in the middle between the two bits.

The second way is the other way around. While it does have fixed lengthsfor every piece of line, it has no signal changes at regular intervals.Consequently, it is possible that the identification decoding methodskips bits, because it has no idea when one bit ends and the otherbegins. It could, in other words, turn 4 ones into 3, without a good wayto detect this error. On the other hand, the second way works with onlytwo levels of thickness, in contrast to the first way with 3 levels.

Since the decoding is meant to be done on digital photographs capturedby a digital imaging device, which can be blurry, partially shadowed,or, more generally, can be of bad quality, working with 3 levelspossibly complicates the decoding of such digital photographs.

c) The third way represent bits combines the advantages of the first andsecond way. It works with only two levels, one representing a bit andthe other the transition to the next bit. The combination of the ‘bit’part and its transition are always the same length. Hence there is asignal change at regular intervals, for example when going from thetransition to the following bit. The difference between a zero and a oneis the length of the parts. For a one, the bit-part is significantlylonger than for a zero. The transition-part of a bit is determined bythe total length for a bit minus the length of the bit part. A signalfor this kind of encoding is shown in FIG. 3.

Note that this third way of representing bits is classified as anunipolar line code.

While other ways of representing bits or N-bit data may be used, thethird way has exactly the properties the identification decode methodneeds.

Error Correcting Codes

Although the third way in this example is chosen to allow easy decoding,it still remains possible that errors are made. Because of the regularsignal changes, missed bits will be rare and can be corrected, buterrors against bit values remain very possible, for example due toimperfections in the photograph. That's why a linear error-correctingcode in this example is added to the encoding process by using a Hammingcode, because of its ease of use and its error-correcting rather thanerror-detecting capabilities. More complex codes, such as the Hadamardcode, may be used. In the example the Hamming(7,4)-code is used with aninformation rate of 57%, An extra advantage of Hamming(7,4)-code is thatmost data consists of bytes, which are 8 hits, so the input data oftenconsists of a multiple of four bits, which can be plugged directly intothe Hamming(7,4)-code. This is, amongst others, the case for ASCIIcharacters, which are each, a byte long, and after encoding them withthe Hamming code are each 14 bits long. For example, the letter ‘A’(capital a) is shown as encoded in a curve in FIG. 5. This letter isASCII (American Standard Code for Information Interchange) character 65,and is represented as a byte as ‘0100 0001’. Using Hamming (7,4)-code,this becomes: ‘1001100 1101001’. This is exactly what is illustrated inFIG. 5.

In coding theory, Hamming(7,4)-code, is a linear error-correcting codethat encodes 4 bits of data into 7 bits by adding 3 parity bits. It is amember of a larger family of Hamming codes.

Enabling Data Decoding

In FIG. 5 the different bits could be read out from left to right, butthis will not always be the case. The image seen in FIG. 5 might beprinted out and hung up upside down or vertical. In order to be able toread and decode a curve, it must he possible to distinguish the endpoint of the curve from the start point of the curve. By adding a headerand a tail to the plurality of N-bits, the read out of the plurality ofN-bits can be done by evaluating the first and last bits. Note that botha header and a tail are necessary, because if only one is used, the datamay be, by coincidence, the same as the header or tail. Furthermore, inorder to decode a curve, one also needs to know what kind of informationis inside the curve. This may be done by adding another 4-bit codewordto the curve, right after the header.

IThe encoding of a content (a string consisting of ASCII characters) inthis example will go through the following steps:

-   1. The ASCII characters are converted to a plurality of 8-bit data.    For example ‘A’ becomes ‘0100 0001’;-   2. The content is prefixed with a header sequence of 4 bits. For    example ‘0100 0001’ becomes ‘0001 0100 0001’-   3. The corresponding tail sequence is added. (‘0001’ has four ones    after encoding, so its tail is ‘0000’), for example ‘0001 0100 0001’    becomes ‘0001 0100 0001 0000’-   4. The whole is encoded with Hamming(7,4)-code, for example ‘0001    0100 0001 0000’ becomes ‘1101001 1001100 1101001 0000000’

The resulting codeword is drawn as on the curve in FIG. 6.

Example of an Identification Decoding Method

An example of a preferred embodiment is detailed as followed:

Pre-Processing a Photograph

In the example the photographs comes in RGB-formats. By differentillumination conditions for the same curve, other colors, otherresolutions, taken from under an angle, the input to the identificationdecoding method can be expected to be very diverse.

In a first stage the photograph (602) of a digital fingerprint code (DFcode) by a digital imaging device is transformed to a binary image(612), using morphological operations. In the example an adaptivethreshold method is used which introduced noise in places without curve.In order to prevent this noise from interfering with the followingoperations, a median blur is performed, to filter out the white spots(622). Because it might be possible that the median blur breaks thecurves at bit transitions, the last step of the processing is to performdilations (632) to connect all bits into one solid curve again. Afterthese steps, it ends up with a binary image that can be used as input tomore general algorithms, that don't need to be concerned about imagedetails.

Finding the Skeleton of the Curve

In order to read out the content of the image captured curve from animage captured digital fingerprint code, one needs to follow the curveand at every point check the thickness of the curve at that point, sincea computer cannot locate the bits easily like a human. Consequently, thenext step in the example is finding the path that goes through themiddle of the curve. It is quite clear that for the purposes of theapplication, the requirement of connectedness in the skeleton is farmore important, because without connectedness, the content in the curvecan not be found. It is found that the thinning algorithm of Zhang-Suengives the best result as thinning method. It always delivers acompletely connected curve, and thus gives a much more reliable androbust alternative to more straightforward methods.

Information about Line Thickness

Since the data is embedded using variable line thickness, there is aneed for a method about the line thickness out of the pre-processedimage, which is the result of the pre-processing of the photograph. Aneasy way to do this is by taking the euclidian distance transformationof the pre-processed image. This changes the value of every pixel to thedistance of that pixel to the nearest black pixel. One can easily see onthe pre-processed image that this value will, in the middle of thecurve, approximate half of the thickness. After that, the curve isfollowed from start to end. At each location of the curve, the value ofthe distance transformation at that pixel location is stored. Thecollection of these values, in the order they are found, can beinterpreted as a one-dimensional signal, varying with the location onthe path. This signal corresponds to the noisy line thickness along thepath, and it is this information that we need to get the embeddedcontent. After reading out the values, they are smoothed by using aone-dimensional median filter in order to remove outliers and enhanceinterpretation.

Turning the Values into Bits

After obtaining the smoothed values, the method of decoding the imagecaptured digital fingerprint code starts interpreting with the peaks inthe one-dimensional signal as bits. In the example it is done in twosteps:

-   a) The peak positions are searched.-   b) decodes to a plurality of N-bit data, which is binary data, by    checking length and width of the peaks

If the plurality of N-bit data is decoded from the image captured curve,the plurality of N-bit data is converted to the content which isembedded in the curve of the digital fingerprint code.

Other Preferred Embodiments

The present invention may comprise thus a two dimensional shaperecognition method, to determine the shape of the digital fingerprintcode but also if a change is found in the determined one-dimensionalsignal, the identification decoder may check the shape that forms thethickness on the location. This may introduce an extra facility to embedextra N-bit data and security in the digital finger print code. Theidentification encoder may therefore select from a number of shapes tochange with the selected shape the thickness of a part in the firstsegment to the determined thickness. A preferred two dimensional shaperecognition method is the SKS algorithm as disclosed in “A ShapeRecognition Algorithm Robust to Occlusion: Analysis and PerformanceComparison” by Karthik Krish and Wesley Snyder, Sep. 13, 2007. But alsoother two dimensional shape recognition methods may be used such asshape context method, Hu Moments method and curvature scale spacematching method.

The thicknesses that form the embedded code on a curve in a digitalfinger print may comprise itself an identification code such as aQR-code, a bar-code or digital finger print code.

The determined image captured curve may be formed by a high contrast inthe image so the determination step for the image captured curve maycomprise a contrast change method to determine a curve in the imagecaptured digital fingerprint code.

The determined curve in the document of the identification encodingmethod is preferable generated by a plane filling line pattern generatorso the determined curve is a plane filling line pattern and morepreferable it is generated by an Lindenmayer system.

Plane Filling Line Pattern

To prevent counterfeiting, geometric repeat patterns are filled in aregion, mostly filled as background pattern, of the document space froma document. The complexity of such geometric repeat patterns is hard toreproduce and thus serve as a security feature. Such geometric repeatpatterns which are filling a region are called a plane filling linepattern.

A plane filling line pattern, which is determined by one or more lines,is a geometric repeat pattern that may fill a region, also called aspace, in the document space of a document. This region can be any shapebut it is totally filled with the plane filling line pattern. Preferablythis region is rectangular shaped. The lines or parts of lines, in aplane filling line patterns may have any colour, thickness or may bedefined as a dashed line. Preferably a plane filling line patterns is asingle line which fills the region.

In a preferred embodiment of the present invention the plane fillingline patterns is a space-filling curve or a FASS curve, a space-fillingcurve, a self-similar fractal curve, a de Rham curve, a space-filingtree, a maze, a fret pattern, a kolam pattern, interlace pattern, or alabyrinth. In the present invention the plane filling line patterns(105) has the constraint to comprise a repeating sub-pattern thatdefines a line, bounded by two distinct end points and preferably theplane filling line pattern, itself, is a line, bounded by two distinctend points.

Interlace patterns are a kind of design, historically used as adecorations in many places and by different cultures, such aseverlasting knots, Celtic knots or Islamic interlace pattern or Croatianinterlace patterns. Interlace patterns are mostly looped, braided and/orknotted.

In the state-of-the-art a plane filling line patterns is generated by aplane filling line pattern generator wherein these geometric repeatpattern, also called a periodic pattern, are generated by softwaremethods which often comprises mathematical methods. In a preferredembodiment the plane filling line pattern generator is aLindenmayer-system.

In the present invention the plane filling line patterns is generatedand determined as a plurality of draw instructions. A draw instructionis an instruction to draw an image in a document space. The image isoften a geometrical primitive such as a point, line, arc, polygon. Adraw instruction may be a vector draw instruction or a straight linedraw instruction. The generated plurality of draw instructions maycomprise also other instructions such as jump to absolute or relativepositions in the document space, storing positions, direction ofdrawing, defined as an angle.

Some examples of computer generated geometric repeat patterns areTaprats™ (http://sourceforge.net/projects/taprats) for Islamicinterlacing pattern, Knotter™ (http://sourceforge.net/projects/knotter)for Celtic Knots, Amaze™ (http://sourceforge.net/projects/qtamaze) formaze generation. A Kolam pattern generator is disclosed in ROBINSONTHAMBURAJ. Extended Pasting Scheme for Kolam Pattern Generation. FORMA.2007, vol. 22, p. 55-64.

The generated plane filling line pattern after the overlaying may beclipped and/or scaled to a determined region from the document space ofthe security document. The determined region may be any shape.

The lines in a plane filling line patterns and the lines in thedetermined graphic object (205, 207) in the present invention havepreferably a thickness between 1 82 m and 10 mm. Smaller the thicknessof these lines more difficult to counterfeit the security document.

The minimum distances between the lines in a plane filling line patternsis preferably between 1 μm and 10 mm. Smaller the minimum distancesbetween the lines, more difficult to counterfeit the document.

The spaces between the lines in a plane filling line patterns (105) andthe lines in the determined graphic object in the present invention arepreferably between 1 μm and 10 mm. Smaller the spaces between the lines,more difficult to counterfeit the document.

Lindenmayer System

A Lindenmayer system, also called an L-system, is a parallel rewritingsystem and a type of formal grammar. An L-system consists of an alphabetof symbols that can be used to make strings, a collection of productionrules that expand each symbol into some larger string of symbols, aninitial “axiom” string from which to begin construction, and a mechanismfor translating the generated strings into geometric structures. Thesymbols of the alphabet are preferably vector draw instructions, such asTurtle Graphics and the string generated from the Lindenmayer system isthan a plurality of step-by-step vector draw instructions.

L-systems are disclosed in an electronic version of a book, especiallyin Chapter 1, that was published by Springer-Verlag, New York, in 1990an reprinted in 1996: “The Algorithmic Beauty of Plants” by PrzemyslawPrusinkiewicz, Aristid Lindenmayer.

A pattern generated by an L-system is an advantage to be used assecurity enabled graphic object in a security document to prevent forexample counterfeiting. Because the security pattern is defined bydetermined production rules and determined alphabet, which are difficultto re-engineer on the security pattern itself.

The recursive nature of the L-system rules leads to self-similarity andthereby, fractal-like forms are easy to describe with an L-system, suchas a Hilbert curve or Sierpinski Triangle.

In a preferred embodiment the L-system generates a space-filling curve.Space filling curves are disclosed in is BADER MICHAEL. Space-FillingCurves: An Introduction With Applications in Scientific Computing.Edited by BARTH T. J., et al. SPRINGER, 2012. p. 278. In a preferredembodiment the L-system generates a space filling curve selected fromHilbert curve, Levy C curve, Koch curve, Peano curve, Gosper curve,Dragon curve, Moore curve.

REFERENCE SIGNS LIST

TABLE 1 100 Vertical axis 200 Horizontal axis 300 A plurality of binarydata 500 Digital fingerprint code 406 Value ‘1’ 405 Value ‘0’ 400 Curve602 Image capturing method 605 An image captured digital fingerprintcode 612 Thresholding method 615 An threshold image captured digitalfingerprint code 622 Blurring method 625 A blurred thresholded imagecaptured digital fingerprint code 632 Dilatation method 635 Adilatational blurred thresholded image captured digital fingerprint code900 User interface object 901 User interface object 902 User interfaceobject 903 User interface object 904 User interface object 905 Userinterface object 906 User interface object 907 User interface object 908User interface object 909 User interface object 910 User interface

What is claimed is:
 1. A decorative workpiece comprising: an inkjetprinted wood pattern including an identification code to track-and-tracethe decorative workpiece; wherein the identification code is invisiblewith a human eye at a viewing distance larger than 20 centimeters.
 2. Adecorative workpiece comprising: an inkjet printed wood patternincluding an identification code to track-and-trace the decorativeworkpiece; wherein the identification code is invisible with the humaneye and secret.
 3. The decorative workpiece according to claim 1,wherein the decorative workpiece includes a synthetic core layer.
 4. Thedecorative workpiece according to claim 2, wherein the synthetic corelayer includes foamed polyethylene or foamed polyvinyl chloride, or thesynthetic core layer is a vinyl-based synthetic material layer.
 5. Thedecorative workpiece according to claim 1, wherein the decorativeworkpiece includes a thermosetting resin and wood based core layer. 6.The decorative workpiece according to claim 5, wherein the thermosettingresin is a melamine based resin.
 7. The decorative workpiece accordingto claim 5, wherein the decorative workpiece is selected from the groupconsisting of kitchen panels, flooring panels, furniture panels, ceilingpanels, and wall panels.
 8. The decorative workpiece according to claim5, wherein the wood pattern includes one or more aqueous inkjet inks ona paper substrate.
 9. The decorative workpiece according to claim 6,wherein the decorative workpiece includes a glueless tongue and groovejoint.
 10. The decorative workpiece according to claim 6, wherein theinkjet printed identification code includes a plurality of N-bit datathat represent content.
 11. The decorative workpiece according to claim9, wherein the content includes at least one of a date that thedecorative workpiece was produced and a serial number of the decorativeworkpiece.
 12. The decorative workpiece according to claim 9, whereinthe plurality of N-bit data includes an error-correcting code.
 13. Thedecorative workpiece according to claim 1, wherein the identificationcode is invisible with a human eye at a viewing distance larger than 50millimeters.
 14. The decorative workpiece according to claim 6, whereinthe decorative workpiece is a direct pressure laminate, compactlaminate, or high-pressure laminate.
 15. The decorative workpieceaccording to claim 9, further comprising a protective layer includinghard particles in an amount between 1 g/m² and 100 g/m².
 16. Atrack-and-tracing method for the decorative workpiece according to claim2, the method comprising: decoding the identification code printed onthe decorative workpiece.
 17. A track-and-tracing method for thedecorative workpiece according to claim 4, the method comprising:decoding the identification code printed on the decorative workpiece.